package com.rceeslca.common.utils;

import com.rceeslca.common.validator.AssertUtils;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/**
 * 树形结构工具类
 * @author rceeslca
 */
public class TreeUtils {


    /**
     * 根据pid，构建树节点
     */
    public static <T extends TreeNode> List<T> build(List<T> treeNodes,Long pid){
        //pid不能为空
        AssertUtils.isNull(pid,"pid");

        List<T> treeList = new ArrayList<>();
        for(T treeNode : treeNodes){
            if(pid.equals(treeNode.getPid())){
                treeList.add(findChildren(treeNodes,treeNode));
            }
        }

        return treeList;
    }


    /**
     * 查找子节点
     */
    private static <T extends TreeNode> T findChildren(List<T> treeNodes,T rootNode){
        for(T treeNode : treeNodes){
            if(rootNode.getId().equals(treeNode.getPid())){
                rootNode.getChildren().add(findChildren(treeNodes,treeNode));
            }
        }
        return rootNode;
    }


    /**
     * 构建树节点
     */
    public static <T extends TreeNode> List<T> build(List<T> treeNodes){
        List<T> result = new ArrayList<>();

        //list转map
        Map<Long,T> nodeMap = new LinkedHashMap<>(treeNodes.size());
        for(T treeNode : treeNodes){
            nodeMap.put(treeNode.getId(),treeNode);
        }

        for(T node : nodeMap.values()){
            T parent = nodeMap.get(node.getPid());
            if(parent!=null&&!(node.getId().equals(parent.getId()))){
                parent.getChildren().add(node);
                continue;
            }

            result.add(node);
        }

        return result;
    }

}
